On the surface of hepatocytes, there is a receptor recognizing asialoglycoproteins. The receptor recognizes the galactose residue of asialoglycoproteins, and has a role in the uptake of asialoglycoproteins by hepatocytes (for example, see M. Spiess, “Biochemistry”, 1990, vol. 29, p. 10009-10018).
With such a substrate specificity, it has been studied to improve the liver-targeting of liposomes by way of adding galactose to lipid components of the liposomes. However, none of the studies brought fully satisfactory results (for example, see JP-A H06-271597 and JP-A H09-235392).
On the other hand, in recent years, utilization of a nucleic acid called short interfering RNA (hereinafter referred to as “siRNA”) with RNA interference (hereinafter referred to as “RNAi”) as a medicine is noticed, and is investigated actively (for example, see WO 02/055692 Pamphlet and WO 02/055693 Pamphlet). siRNA is hard to transfer into cells of a human body if it is administrated alone, and it is necessary to administrate siRNA by embedding it in a suitable carrier, or the like.